The present invention relates to a driving mechanism for a door lock and, more particularly, to an adjustable driving mechanism for a panic exit door lock.
A typical panic exit door lock mounted to a panic exit door includes a press bar mounted to a side of the panic exit door and a lock body inside the panic exit door. The lock body includes a latch bolt movable between an extended, latching position and a retracted, unlatching position and a retractor for moving the latch bolt from the extended position to the retracted position. A driving mechanism is operably connected between the latch bolt and the press bar. The driving mechanism includes a draw member abutting the retractor. When the press bar is pressed, the draw bar urges the retractor to move, causing retraction of the latch bolt. However, in a case that the driving mechanism is installed in a position such that a spacing exists between the draw member and the retractor, the draw member travels idly through the spacing without moving the retractor when the press member is pressed. As a result, the latch bolt can not move to its fully retracted, unlatching position, adversely affecting operation of the door and requiring troublesome reinstallation of the driving mechanism.
U.S. Patent Publication No. 2009/0266120 A1 discloses an adjustable driving mechanism to solve this problem. The adjustable driving mechanism includes a bracket fixed to a door. A draw member includes a first end pivotably connected to the bracket and a second end connected to a retractor. A linking rod is connected between the draw member and an operative member mounted to the door such that operation of the operative member causes movement of the linking rod and pivotal movement of the draw member, which in turn, urges the retractor to move a latch bolt from an extended position to a retracted position. A follower is movably mounted to the linking rod. An adjusting member is in threading connection with the follower and rotatable to move the follower relative to the linking rod to adjust a position of the second end of the draw member relative to the retractor. However, unlatching operation of the operative member is not force-saving and not smooth. Specifically, the first end of the draw member is not movably connected to the bracket, and a spacing between a pivot point defined in the first end of the draw member and a force applying point defined by a coupling point of the linking rod and the draw member is much smaller than a spacing between the force applying point and a contact point of the second end of the draw member and the retractor, so that a user has to apply large force to press the operative member to move the latch bolt from the extended position to the retracted position, causing inconvenient operation for unlatching the latch bolt.
Thus, a need exists for an adjustable driving mechanism for a panic exit door lock such that the position of the draw member relative to the retractor can be adjusted to avoid troublesome reinstallation of the driving mechanism while allowing easy and smooth unlatching operation.